Neuronal survival and neurite elongation, two key components of neural regneration, are likely to depend on the availability to the neurons of appropriate trophic stimuli. Nerve Growth Factor has served for 30 years as a model for such neuronotrophic factors. We have recently identified a new ciliary neuronotrophic factor CNTF, directed to the cholinergic neurons of chick embryo ciliary ganglia, in the extract of intraocular tissues that these neurons innervate. Other neuronotrophic activities have been observed in several tissue extracts and conditioned media, which address neurons from several ganglia (GNTFs) or from spinal cord (SC-NTFs). Polyornithine-binding neurite-promoting factors (PNPFs) have also been recognized and partially purified from such conditioned media. We plan to continue the investigation of these several factors, particularly through the use of monoclonal antibodies.